The present invention relates to a nozzle structure in an electromagnetic fuel injector for use with an engine.
Such a nozzle structure is disclosed in Japanese Patent Laid-open Publication No. 63-50667, for example. A nozzle disclosed in the prior art is employed in an electromagnetic fuel injector for intermittently injecting a liquid fuel from an injection hole by reciprocating a valve movable by a magnetic attraction force due to excitation of a solenoid coil and a reaction force of a spring. The nozzle to be mounted on the front side of the injection hole includes a central columnar portion of a circular cone and three or more atomizer holes arranged about a central axis of the columnar portion at circumferentially equal intervals in such a manner as to be inclined radially outwardly from the central axis of the columnar portion. The columnar portion is formed at its top with a fuel colliding portion against which the fuel injected from the injection hole collides. The fuel colliding portion has a given cross-sectional area in a direction perpendicular to the central axis of the columnar portion. With this structure, the fuel columnarly injected from the injection hole collides with the fuel colliding portion formed at the top of the columnar portion of the nozzle, thus atomizing the fuel and injecting the atomized fuel through the atomizer holes to a given external circular area.
The atomizer holes of the nozzle is formed normally by machining so as to meet a high accuracy, and the fuel colliding portion of the nozzle is accordingly formed by shot blasting the top of the circular cone.
However, in the conventional nozzle having the fuel colliding portion formed by shot blasting, it is hard to suppress variation in shape or size of the fuel colliding portion due to the machining accuracy of the atomizer holes and the shot blasting, causing a problem that the execution of fuel atomization is influenced by the size of the fuel colliding portion. Even in the case that the fuel is atomized, there occurs variation in an atomized condition of the fuel.